Island in Shark Bay off the WA coast to create a new colony of the highly endangered marsupials.

The Bettongs have been breeding in Heirisson Prong, a peninsula sanctuary on the mainland. Their new home, Faure Island, is managed by the Australian Wildlife Conservancy.

Bettongs are a small 'rat kangaroo', standing about 20cm tall. "In many ways they are very rabbit-like in their size and the way they burrow," said Dr Jeff Short, Principal Research Scientist with CSIRO Sustainable Ecosystems. Dr Short is based in Perth but also works at Useless Loop, Shark Bay.

Bettongs are also known as 'boodies', the South Western Aboriginal name for the marsupial, said Dr Short.

The researchers were originally hoping to trap and send a group of about 30 animals, but could only capture 17. They were trapped and put into cages so they could be sent by light aircraft to nearby Monkey Mia where they were put on a boat to Faure Island and released.

"We had a preferred sex ratio of the group, which consisted of two females to each male to boost the population," explained Dr Short. The ratio of the group ended up being nine males to eight females.

Bettongs breed continuously throughout the year having a single offspring at a time. "We occasionally have twins," said Dr Short. "But it is very rare." Most females have two offspring a year, but with a gestation period of 115 days, it is possible for them to have three in a good year.

A square kilometre can support about 15 Bettongs. Faure Island is 50 square kilometres, so it is possible the original population of 17 can swell to about 2000 animals if everything goes well. "It is an important new site," he said. "We don't have the worry of new predators."

Bettongs once dug their burrows over two thirds of mainland Australia, but cats and foxes hunted them to extinction on the mainland. They were also considered a pest to agriculture.

"In New South Wales alone, nearly three million bettongs were harvested between 1883 and 1920," said Dr Short.

Fortunately the species survived on three islands off the Western Australia coast. Approximately 7,000 animals in total lived on the islands according to a consensus done in the late 1980's and early 1990's said Dr Short.

Ten years ago CSIRO transferred 12 bettongs from Dorre Island in Shark Bay to Heirisson Prong on the nearby mainland - 30 years after they were last present on the mainland. Since then the population at Heirisson Prong has swollen to 1000 animals.

The Heirisson Prong has a narrow neck making it easy to fence off. There is also a continual baiting program to ensure feral animals don't stray into the area. In addition, an attracting/trapping program has managed to rid the area of cats and foxes. In 1993-94, 60 cats and 25 foxes were removed by traps from a 50 square kilometre area.

The Heirisson Prong Project is a cooperative conservation project providing threatened mammals with a foothold on the Australian mainland. The project won the 2001 Banksia Gold Award.

The project was initiated in 1989 by Useless Loop, a local salt-mining community, in partnership with CSIRO and the mining company Shark Bay Salt Joint Venture. The Earthwatch Institute joined as a partner in 1995.